Fig. 5

View of the PbLSD seven-blade propeller fold (a) 4-His-Fe unit (b). In panel a, the single subunit is oriented to show the seven blades (numbered) with the electron density of the 4-His-Fe unit visible in the center. In panel b, the subunit is rotated to view the 4-His-Fe unit modeled into the Fo-Fc omit electron density map. The Fo-Fc omit electron density maps in panels a and b at 7.0 σ were calculated without the four histidines, iron and the waters in the model. The water forming the 5th coordination site, is represented by a small ball surrounded by density in the image, while the iron is represented by a larger central ball. Thr122 is proposed to occlude the 6th Fe coordination site